Perrhenic acid

Perrhenic acid
	Monohydrate
Names
	IUPAC name Perrhenic acid
	Systematic IUPAC name [Diaquatrioxidorhenium(VII)]-μ-oxido-[trioxidorhenium(VII)]
	Other names Hydrated rhenium(VII) oxide
Identifiers
CAS Number	13768-11-1 ;
3D model (JSmol)	Interactive image;
ChemSpider	21106462 ;
ECHA InfoCard	100.033.968
EC Number	237-380-4;
PubChem CID	83718;
RTECS number	TT4550000;
CompTox Dashboard (EPA)	DTXSID80894065 ;
	InChI InChI=1S/2H2O.7O.2Re/h21H2;;;;;;;;; Key: JOTGKJVGIIKFIQ-UHFFFAOYSA-N ; InChI=1/2H2O.7O.2Re/h21H2;;;;;;;;;/rH4O9Re2/c1-10(2,3)9-11(4,5,6,7)8/h4-5H2 Key: JOTGKJVGIIKFIQ-SEUCOXMMAB;
	SMILES [OH2+][Re-2](=O)(=O)(=O)([OH2+])O[Re](=O)(=O)=O;
Properties
Chemical formula	H4Re2O9 (solid); HReO4 (gas)
Molar mass	251.2055 g/mol
Appearance	Pale yellow solid
Boiling point	sublimes
Solubility in water	Soluble
Acidity (pKa)	−1.25
Conjugate base	Perrhenate
Structure
Coordination geometry	octahedral-tetrahedral (solid); tetrahedral (gas)
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H314, H332
Precautionary statements	P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P330, P363, P405, P501
NFPA 704 (fire diamond)	3
Flash point	Non-flammable
Related compounds
Related compounds	Perrhenate; Manganese(VII) oxide; Technetium(VII) oxide; Rhenium(VII) oxide; Permanganic acid; Pertechnetic acid; Perchloric acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Perrhenic acid is the chemical compound with the formula Re₂O₇(H₂O)₂. It is obtained by evaporating aqueous solutions of Re₂O₇. Conventionally, perrhenic acid is considered to have the formula HReO₄, and a species of this formula forms when rhenium(VII) oxide sublimes in the presence of water or steam. When a solution of Re₂O₇ is kept for a period of months, it breaks down and crystals of HReO₄·H₂O are formed, which contain tetrahedral ReO−4. For most purposes, perrhenic acid and rhenium(VII) oxide are used interchangeably. Rhenium can be dissolved in nitric or concentrated sulfuric acid to produce perrhenic acid.